1. Field of the Invention
The present invention relates to a motorcycle that has a clutch driving device for driving a clutch and a shift driving device for driving a transmission.
2. Description of the Background Art
The AMT (Automated Manual Transmission) mechanism is conventionally proposed as a system that automates the switching (shifting) of the gear ratio of the transmission of a motorcycle and the connecting and disconnecting of the clutch. The AMT mechanism involves a shift actuator for driving the transmission and a clutch actuator for driving the clutch (see JP 2003-320861A).
In the motorcycle having the AMT mechanism disclosed in JP 2003-320861A, the shift actuator and the clutch actuator are positioned behind the cylinder block of the engine and above the transmission. Positioning the actuators near the engine in this way prevents the actuators from touching the ground during cornering of the motorcycle. This avoids reduction of the bank angle during cornering and prevents damage to the AMT mechanism when the motorcycle falls over.
However, in this conventional motorcycle, the provision of the shift actuator and clutch actuator near the engine allows direct cause heat and vibrations generated by the engine to be conducted to the actuators.
In particular, with a hydraulic shift actuator, the shifting operation is achieved by rotating the shift spindle of the transmission by predetermined angles with the pressure of the operating oil. Smoothly performing the shifting operation requires rotating the shift spindle accurately by the predetermined angles. However, when heat and vibrations are applied to the actuator, temperature and pressure variations of the operating oil and vibrations of mechanical components vary the timing and amount by which the actuator drives the shift spindle, which lowers the accuracy of the control of the shift spindle by the actuator. This makes it difficult to achieve the shifting operation smoothly. Also, heat and vibrations promote deterioration of the actuator.
With an electrically-driven shift actuator, the shifting operation is achieved by rotating the shift spindle of the transmission at given angular intervals with power from an electric motor. Smoothly performing the shifting operation requires accurately controlling the electric motor through signal lines to rotate the shift spindle accurately at the given angles. However, when heat and vibrations are applied to the actuator, the signal lines may be cut by vibrations and the signals may be varied by heat, and the efficiency of the electric motor is lowered by heat and vibrations. Furthermore, heat and vibrations promote deterioration of the actuator.
As a result, the operation of the actuator becomes unstable and the durability of the actuator is reduced.
Furthermore, the piping and wiring for the shift actuator are provided around the engine, which complicates the piping and wiring structure around the engine and involves troublesome work in attaching the actuator and fitting the piping and wiring. Moreover, the complicated piping and wiring structure around the engine increases the weight of the motorcycle.